Seating structures may be configured with flexible backrest members, such as polypropylene sheets and woven elastomeric membranes. Typically, the flexible members are put in tension in various ways so as to provide the flexible member with a three-dimensional contour. For example, a peripheral frame may surround and hold the flexible member. In other devices, various portions of the flexible member are held at spaced apart locations, with an intermediate member pushing on the flexible member to form the flexible member and to put portions thereof in tension. Such systems may provide undesirable hard contact points, whether by contact with the frame or by contact with the intermediate member.